The present invention relates to a pressure filter apparatus and, more particularly, to a filter media mounting assembly in a pressure filter.
In the type of pressure filter to which the present invention relates, a filter vessel is provided having a top cap structure and a bottom valve structure joined by a porous filter screen, generally cylindrical in structure. Liquid to be filtered usually containing suspended solids is inlet into the vessel and allowed to rise to a desired height. The vessel is pressurized to force the liquid through the filter screen. Upon cessation of liquid flow into the vessel, the pressurization is continued to force the liquid through the filter screen and, accordingly, the liquid level drops in the vessel. The filtered liquid is discharged from a cavity surrounding the filter screen. The buildup of suspended solids on the filter screen, which can form a cake hardened by the pressurization within the vessel, is broken from the filter screen by one or more methods and released from the vessel through the bottom valve structure.
Frequently it is desirable to affix a filter media sleeve inside the filter screen to assist in filtering the liquid. The filter media most often comprises a cylindrical sleeve fitted within the filter vessel adjacent the inside edge of the filter screen. Various methods were used to seal such media to the inside wall of the vessel, none of which has yet proved entirely satisfactory. One method is to utilize two rigid metal hoops of a diameter nearly equal to that of the filter vessel. Such hoops are bolted together with one edge of the media therebetween. This arrangement has not provided a liquid tight seal between the filter media and the inside wall of the vessel, which is necessary to assure that no liquid to be filtered can bypass the filter media. Further, such metal hoops are awkward and heavy, making the installation and removal of the media difficult. The hoops, because of their diameter nearly equal to that of the filter vessel, also require a hatch in the top section of the vessel of the full diameter of the vessel to permit installation and removal of the hoop and media. Such a hatch is expensive and quite heavy, usually requiring a crane to open.